1. Field of the Invention
The present invention generally relates to a charge-coupled device (i.e. CCD) delay device which is used to delay an analog signal such as a video signal or the like and, more particularly, is directed to an input circuit for a CCD delay line.
2. Description of the Prior Art
A recent television receiver or the like utilizes a CCD delay device formed of a CCD delay line to delay an analog signal such as a video signal and so on. In the CCD delay line of the gate input type, when an input signal of a large level (e.g., level slightly higher than the level corresponding to the maximum amount of charges that the CCD delay line can treat) is supplied thereto, an overflow of charges occurs in a charge transfer portion of the CCD delay line, which leads to various disadvantages. In order to avoid the charge overflow, it is proposed in the prior art to limit the level of the input signal by a limiter circuit provided independently of the CCD delay device.
However, in accordance with this previously-proposed method in which the limiter circuit is provided independently of the CCD delay line to limit the level of the input signal, the maximum amount of charges treated by the CCD delay line is different depending on the characteristic of the CCD delay line so that the limiting level of the limiting circuit must be adjusted in response to CCD delay lines, which is very cumbersome.
Furthermore, the CCD delay line has a temperature characteristic such that when the temperature is changed, the level K controlled by the limiting circuit and the maximum treating charge amount input to the CCD delay line are not equal to each other to generate a difference. This difference will cause the overflow of charge if the change of temperature is too large.